You can hook up an inverter by plugging it into one of the 12 Volt outlets located on the dash and inside the console in the 2004. I believe these are fused at 10 amps, so you can't power anything that draws more than about 100 watts.

You can connect a larger unit directly to your 12 Volt battery. But be sure to use a fuse in the line.

Don't use any 12 Volt accessories for long if the car is not in Ready mode. The 12 Volt battery is small and will quickly run down. When the car is in Ready mode, it is recharged from the High Voltage battery.

Don't even think about hacking into the high voltage system to run an inverter. That stuff is DANGEROUS! The Prius has a lot of safety devices built in, and if you bypass them to get to the high voltage, you're just asking for trouble.

Most electrical supply stores such as Radio Shack carry inverters.

Mike RT